Kidney Stones Flashcards
Types of kidney stone
Calcium oxalate stones (most common)
Uric acid
Struvite (infection)
Cysteine
Name three sites where renal stones cause obstructions
Pelvic-ureteric junction of the kidney
Pelvic brim
Ureterovesical junction
Bladder urethra outlet
Causes of urinary tract stones
Dehydration
Hyperoxaluria
Hypercalcemia
Hypercalciuria
Infection
Cysteinuria
Renal disease (polycystic kidneys)
Drugs
How are renal stones formed?
Urine is normally supersaturated with ions and stone-forming substances, however inhibitors in the urine prevent crystal formation which leads to stones.
Impairment of inhibitors that prevent crystallization/ concentrated urine due to dehydration favour crystal formation.
Crystals form and aggregate together in the urine. These then become trapped in the urinary tract and enlarges. Flow of urine is therefore key to preventing stones.
Causes of hypercalcaemia
Hyperparathyroidism
Malignancy
Idiopathic
Sarcoidosis/TB
Causes of hyperoxaluria
Primary: AR metabolic defects in oxalate biosynthesis
Secondary: Diet (spinach, rhubarb, tea), GI disease
Nephrocalcinosis
Diffuse renal parenchymal calcification. Typically painless. Causes hypertension and CKD.
Caused by renal nexrosis, hypercalcaemia, tubular acidosis.
Uric acid stones
Uric acid is the endpoint of purine metabolism. Hyperuricaemia can occur due to gout, due to increased cell turnover (myeloproliferative disorders), as a consequence of chemotherapy or dehydration.
Increaased uric acid excretion in the urine occurs, which can cause stone formation.
Struvite stones
Stones composed of phosphate, magnesium, ammonium and calcium. Struvite stones are often large - form staghorn calculus.
Occur in association with UTIs by urea-splitting bacteria e.g. Klebsiella, Proteus, Pseudomonas. Urine becomes alkaline due to the formation of ammonia. Availability of ammonium ions and alkaline pH favours stone formation. Increased mucoprotein production creates an organic matrix which stones can form on.
Cysteine stones
Caused by renal tubular defects. AR disorder affects amino acid transport. Cysteine is nor reabsorbed and it is crystalizes in the urine.
Risk factors for struvite stones
Risk factors related to risk of UTI
Female
Catheters
Stagnant urine
Urinary tract abnormalities
Causes of bladder stones
Caused by bladder outflow obstruction or presence of a foreign body
Bacteriuria is usually found in patients with bladder stones. Some stones that have passed down from the upper urinary tract.
Complications of renal stones
Stones may be located in the renal parencyma or collecting system. Obstructs urinary flow, causing hydronephrosis.
Pressure necrosis from a calculus can cause damage to the renal parenchyma.
Stones may ulcerate through the call of the collecting system.
Presentation of renal stones
Pain radiating from the flanks to the iliac fossa and testis/labia (distribution of L1).
Haematuria
Pallor, sweating, vomiting
Irritative voiding symptoms
Patient presents with acute flank pain , pallor and vomiting. Give 4 differential diagnoses
Renal colic due to stones Pyelonephritis AAA Pancreatitis Diverticular disease
